This invention relates to a process for the carbonylation of an organic halide, wherein the halogen values generated by such process are recovered in a usable form.
Heck, U.S. Pat. No. 3,988,358 (incorporated herein by reference) discloses a process for the preparation of carboxylic acid esters from organic halides, which comprises carbonylation of an organic halide in the presence of a palladium catalyst and a tertiary amine. Heck, U.S. Pat. No. 3,960,932 (incorporated herein by reference), discloses the preparation of aldehydes by reacting organic halides with carbon monoxide and hydrogen in the presence of a basic tertiary amine and a palladium metal catalyst. Heck, U.S. Pat. No. 4,128,554 (incorporated herein by reference), discloses the preparation of carboxylic acid amides by reacting an organic halide with a primary or secondary amine with carbon monoxide, in the presence of a palladium catalyst and a tertiary amine. It is disclosed that the tertiary amine is necessary to make the catalyst catalytic under the reaction conditions, and that the tertiary amine further acts as an acid acceptor to tie up the halides formed during the reaction. The problem with this process is that it is very hard to recover the halogen values from the salt prepared from the tertiary amine and the halogen. Some suggested processes for recovering the halogen values involved attempting a thermal cleavage between the amine and the halide values. The problem with this approach is that in most cases the temperatures necessary to achieve the thermal cleavage result in significant decomposition of the amines, driving up the costs of such a recovery.
What is needed is a process for the carbonylation of organic halides, wherein the halogen values generated by the process can be recovered in an efficient and reasonably economic manner.